TPS61094: Buck/Boost Supercap charger

Hi Abhinav,

The buck mode is used to charge the supercap.

The Vout is either bypassed from the Vin or boosted from the supercap.

Let me comment together with your design:

• Vin = 5V (+/- 0.5V), Vout target = 3.8V, Vcharging = 3.7V (no option for 3.8V), Vsupercap = 2.5V is OK.
• Suppose it is configured as auto buck or boost mode, then the device works as below:
  • When the 5V Vin is present, then the Vout is also 5V. The buck mode will be active to charge the supercap. The max charging voltage and current are decided by the resistors at the VCHG and ICHG pins.
  • If the 5V Vin is not there, then the boost mode will be active. The Vout will be 3.8V, which is boosted from the supercap.

Regards

Lei

I am using 1S 3.6V LiSoCl2 battery as the main power source for my data logger. This battery max continuos current is around 200mA. 

There will be MCU, sensors, storage IC, and modem.

For a modem that requires a high current burst during transmission, I want to use a 1S lithium ion supercapacitor to support the modem's high current demand.

The TPS61094 is complex for me as I am new to electronics. So I was wondering if I could use this IC only to charge the supercapacitor.  I will do the power path manually. I will check the voltage for capacitor and the battery separately and ENABLE the charging manually. 

Focus here is to do charging the Supercapacitor.

There will be time when Battery LiSOCl2 voltage is higher than supercapacitor's voltage. Here, we need to have buck regulator. I can see that the TPS61094 support buck regulation.

And there will be time when Battery LiSOCl2 voltage may be lower than the supercapacitor. If that happen we should have boost, right?

Does TPS61094 able to change the topology for charging the supercapacitor automatically?

TLDR: 

1. Vin: 1S LiSOCl2 Nominal 3.6V 
2. Vsup: 2.5~3.8V 
3. Icharge: 100mA

Please advise. Better yet, what do you think of this IC for my case?

Thank you.

Hi Abhinav,

Let me check and reply to you by tomorrow.

Regards

Lei

Hi Abhinav,

The TPS61094 can be configured in forced buck mode to charge the super cap from 1S 3.6V LiSoCl2 battery.

Please note that the max charge voltage (the Vsup) will be a little lower than the LiSoCl2 battery.

What's the input voltage for the MCU, sensors, storage IC, and modem?

And what's the high current burst during transmission for the modem?

I'm asking because I'd like to check whether the TPS61094 can be configured more powerful. 

Regards

Lei

Lei Zhong said:

What's the input voltage for the MCU, sensors, storage IC, and modem?

The voltage is regulated to 3.3V for MCU, Sensors, Storage IC.

But for the modem will get direct voltage from the capacitor that is charged to 3.7V. No regulator. It can accept from 3.4V to 4.2V.

Lei Zhong said:

And what's the high current burst during transmission for the modem?

2Amp

Hi Suhaimi,

Thanks for providing the information.

Here are the concerns I've seen:

• If powered by a 1S 3.6V LiSoCl2 battery, which is also the power to charge the super cap, then ideally the max charge voltage is 3.6V(won't be higher than the input voltage). That means, the super can can only drop from 3.6V to 3.4V to make the modem work.
• If the voltage of the LiSoCl2 battery drops below 3.4V, then the super cap can't be charged to high enough to make the modem work.

Here is a possible solution for the modem for your reference

Regards

Lei